30 
same. I know you do not believe in it 
very much, and I have my doubts about 
it, although I am doing a little of it just 
now. 
Of course, all of us can point out in- 
numerable cases of filling trees with con- 
crete which have turned out badly, but 
those are usually cases where the job has 
been done with obvious and glaring in- 
efficiency. As you know, of late years a 
crop of “tree doctors” has sprung up in 
the land, and some of them are doing 
work which at least looks as though it 
might turn out all right. I mean the cavi- 
ties are well cleaned out, treated with an- 
tiseptics, re-enforced with iron rods, bolts, 
nails, wire, etc., the concrete is accurately 
adjusted to the cambium line (neglect of 
this seems to be the most obvious fault 
of the old-time jobs), drainage channels 
are cut in the wood, and much other in- 
genuity of various kinds is exercised in 
doing the work. Now, disregarding the 
old-time jobs, which are hardly worth dis- 
cussing, have you or anyone else observed 
fillings made as long ago as, say, ten years, 
but in accordance with what we may term 
modern approved methods? If so, what 
have you discovered? The new growth 
may be rolling nicely over the filling, but 
how about the inside of the cavity? The 
mere fact that new growth over the fill- 
ing is taking place is no proof that decay 
is not going on inside of the tree as fast 
as ever, and the external evidence of good 
health and security may be only a sham. 
I have recently dug out one not very large 
filling in an English elm, over which the 
new growth had been growing nicely for 
some years, and found a surprising 
amount of active decay going on inside. 
How well the cavity had been cleaned out 
in the first place I could not say. 
The feeling that I have about this whole 
matter is that it is easy enough for the 
“tree doctors” to talk glibly, and to say 
that this and that should be avoided and 
that this and that should be done, and all 
will be well. But is it possible to keep 
out the moisture from a filled cavity? Is 
it possible to prevent decay by this 
method? To get back to the question put 
in the first part of my letter — can the op- 
eration be done successfully or is it in- 
herently wrong? 
I should be glad to get many answers 
to my questions. Hans J. Koehler. 
Soil Improvement Office, 
Boston Common, Boston, Mass. 
* * * 
In an article entitled “What We Really 
Know About Tree Surgery,” in Country 
Life in America for December, 1910, Sec- 
retary Levison says on this subject: 
“Cavity filling is necessitated by Improper tree 
pruning and neglect in dressing wounds. Where 
the trees have been properly cared for from their 
early start, cavity filling baa no place at all. In 
old neglected trees, cavity filling is Justifiable only 
where it can serve the practical purpose of elimi- 
PARK AND CEMETERY. 
nating moisture and where every trace of diseased 
wood can be thoroughly removed before the filling 
is inserted. To insure a perfect filling the operator 
or consulting forester must be able to tell whether 
the disease has permeated the whole tree or is still 
in its first stages. He must know whether the dis- 
ease prefers dead wood, or live wood, or both; 
whether it is apt to attack the neighboring trees 
of another species, and whether it is preferable to 
sacrifice the whole limb or tree instead of filling 
it. He must be able to recognize the presence of 
the fungus fibres (mycelia) in order to know when 
to stop cutting into the cavity, and he must know 
how to destroy the various insect enemies found 
within the cavity. He must know whether the wood 
is naturally strong and pliable or soft and brash in 
order to determine the extent to which he can chisel 
into the cavity with safety. He must judge 
whether an ordinary filling will hold or whether 
there is a call for special re-enforcements and me- 
chanical devices such as tin plates over the cement 
to hold the filling in a swaying young tree, or iron 
bars to hold the filling between two split limbs. 
Finally, a knowledge of the nature of the species 
and general condition of the tree in question will 
be serviceable in deciding the future possibility of 
the tree after treatment. These foregoing observa- 
tions are all necessary before the actual filling- 
process is commenced, and in addition to them I 
want strongly to emphasize the fact that, similar 
to the cancerous growth of a human being, there 
are thousands of minute fibres radiating through 
the wood of the tree from the centre of disease, 
and unless every bit of this infested wood is elim- 
inated the work will fail. Moreover, the filling 
must serve the practical purpose of preventing 
moisture from collecting in one place, and, in case 
of diseased hollow trunks, perpendicular shallow 
wounds, and similar instances, the attainment of 
these conditions is frequently impossible. When 
this is the case, the chisel, gouge, and coal-tar, 
without the filling, are the better and cheaper medi- 
ums of prolonging the life of the tree, and in 
many instances the axe is the only alternative. 
Where, however, a filling can be put in with ad- 
vantage, the process should consist in removing all 
diseased wood from it with the free use of the 
knife, chisel, or gouge. It is far better to enlarge 
the cavity by cutting out every bit of diseased 
wood than it is to leave a smaller hole in an un- 
healthy state, for every trace of disease left with- 
in the cavity will continue its destructive work be- 
hind the filling and later on destroy the tree just 
the samej as if there had been no filling at all. 
Where there are boring insects within the cavity, 
their destruction must be assured before filling 
is commenced. It frequently happens with large cavi- 
ties and hollow trunks that the boring insects can- 
not be reached individually by hand, and in such 
eases an original method of fumigating the cavity 
has been resorted to by the writer, which consists 
in closing all orifices leading to the cavity with 
tar paper and then filling it with vapor of hydro- 
cyanic acid gas or with that of carbon bisulphide. 
Either of these gases will kill all animal life and 
will penetrate the exterme burrows which the op- 
erator’s syringe or knife could never reach or 
which might have otherwise escaped his eye. When 
the cavity is absolutely freed from disease and in- 
sects its walls should be washed with corrosive sub- 
limate and covered with white lead or with Bor- 
deaux mixture. The interior should then be stud- 
ded with nails and solidly filled with bricks, stones, 
and cement, or with charcoal, bricks, and cement. 
When that is done, the outer edge of the cavity 
is iuterlaced with wire to assist in holding the 
solid material in place, and a layer of cement, 
mixed one-third sand, is then placed over the wire. 
When dry, this layer should be covered with coal- 
tar. The exposed face of the filling must net be 
brought out to the same plane with the outer bark 
of the tree, but should rather recede a little be- 
yond the growing tissue which is situated imme- 
diately below the outer bark. By this method, the 
growing tissue will be enabled to extend over the 
cement and cover the whole cavity, if it be a 
small one, or else to grow out sufficiently to over- 
lap tbe filling and hold it as a frame holds a pic- 
ture. The growth of this living tissue can be much 
accelerated by cutting around the border of the 
orifice immediately before the season of growth 
commences. Of the many failures in filling cavi- 
ties, the great majority are due to an incomplete 
removal of diseased woods, to the cement being 
flushed out to the surface of the outer bark, or to 
the want of tar on the outer surface of the filling.” 
SPRAYING DEVELOPMENTS IN MASSACHUSETTS 
'■Solid Stream versus Mist. A Brief Statement of the Writer’s 
Experience and Observation During the Last Six Years. 
By R. W 
Arnold Arboretum, 
Spraying operations in Massachusetts 
fall naturally into two groups, namely, 
orchard spraying and woodland spraying. 
Orchard spraying has received a tremen- 
dous impetus throughout the country dur- 
ing the last ten years. This has been due 
to the great and increasing interest which 
is being taken in orchard planting and in 
country-life affairs generally. We are on 
the rise of an agricultural tide in this 
country ! There never was such activity 
in all lines of agricultural practice and 
research as at the present time. Partic- 
ularly is this true of the whole field of 
plant protection, including both insect 
pests and plant diseases. There is the 
keenest kind of interest manifested in 
these lines of inquiry, not only by our 
governmental departments and our agri- 
cultural colleges and experiment stations, 
but also by horticultural and agricultural 
clubs and societies and by public-spirited 
individuals, and most recently by practical 
business firms whose interests are directly 
or indirectly affected by improved meth- 
ods of prevention and control. 
In Massachusetts orchard spraying has 
had the additional incentive of the won- 
derful results which have attended recent 
. CURTIS, 
Jamaica Plain, Mass. 
development in woodland spraying in this 
part of the country. At this writing I 
will first explain this rapid development of 
woodland spraying, then describe a typical 
spraying outfit suitable for orchard and 
light woodland spraying, and conclude with 
some specific directions for the more com- 
mon park and orchard insect troubles. 
Spraying in Massachusetts is performed 
by three general types of machines. There 
are low power, semi-high power and high 
power. 
The low-power machine is operated by 
hand or power up to two and one-half 
horsepower. It produces a mist spray and 
is the most common orchard type ma- 
chine today. The mist is produced at 
close range, i. e., four or five feet from the 
nozzle, by using a very small hole with a 
disc or other device for spreading the 
spray. Such a mist requires a pressure of 
ISO pounds and consumes the least amount 
of solution of any known spray. This 
type of spray was in common use fifteen 
years ago for both orchard and woodland 
work. Spraying in woodlands with such 
a machine involved much climbing and 
ladder work and was both very slow and 
very expensive. 
